1. Field of the Invention
Embodiments of the invention relate to a stereoscopic image display and a method of driving the same.
2. Discussion of the Related Art
A stereoscopic image display is divided into a display using a stereoscopic technique and a display using an autostereoscopic technique.
The stereoscopic technique, which uses a parallax image of left and right eyes of a user with a high stereoscopic effect, includes a glass method and a non-glass method which have been put to practical use. In the glass method, a left and right parallax image is displayed on a direct-view display or a projector through a change in a polarization direction of the left and right parallax image or in a time-division manner, and a stereoscopic image is implemented using polarization glasses or liquid crystal shutter glasses. In the non-glass method, generally, an optical plate such as a parallax barrier and a lenticular lens separates an optical axis of the left and right parallax image, and a stereoscopic image is implemented.
U.S. Pat. No. 5,821,989 and US Publication No. 20070229395A1 are known to disclose an example of the glass type stereoscopic image display.
FIGS. 1 and 2 schematically illustrate a glass type stereoscopic image display. In FIGS. 1 and 2, a black region of a liquid crystal shutter glasses ST represents a shutter that blocks light traveling toward an observer (i.e., viewer), and a white region of the liquid crystal shutter glasses ST represents a shutter allowing transmission of light toward the observer.
FIG. 1 illustrates a time-division operation of left and right images when an impulse type display device DIS1 is selected in the glass type stereoscopic image display. In the impulse type display device DIS1 such as a cathode ray tube (CRT), immediately after data is completely written in a scanning direction, data of each pixel is erased.
In the stereoscopic image display illustrated in FIG. 1, during odd-numbered frame periods, a left eye shutter of the liquid crystal shutter glasses ST is open, and left eye image data RGBL is sequentially scanned on the impulse type display device DIS1. During even-numbered frame periods, a right eye shutter of the liquid crystal shutter glasses ST is open and right eye image data RGBL is sequentially scanned on the impulse type display device DIS1. Accordingly, the observer can view only a left eye image during the odd-numbered frame periods and a right eye image during the even-numbered periods, thereby feeling stereoscopy.
FIG. 2 illustrates a time-division operation of left and right images when a hold type display device DIS2 is selected in the glass type stereoscopic image display. In the hold type display device DIS2 such as a liquid crystal display (LCD), data written in pixels is hold until such time as data is written on a first line during a next frame period following a response completion time point after the data is written on the entire pixels because of to response time delay characteristics.
In the stereoscopic image display illustrated in FIG. 2, during an nth frame period, where n is a positive integer, the left eye shutter of the liquid crystal shutter glasses ST is open and left eye image data RGBL(Fn) is sequentially scanned on the hold type display device DIS2. While the left eye shutter of the liquid crystal shutter glasses ST is open, some pixels, to which the left eye image data RGBL(Fn) of the nth frame have not been written yet in the hold type display device DIS2, hold right eye image data RGBR(Fn−1) which had been already charged in an (n−1)th frame period. Accordingly, the observer can view an image of the right eye image data RGBR(Fn−1) of the (n−1)th frame as well as an image of the left eye image data RGBL(Fn) of the nth frame with his left eye during the nth frame.
In the stereoscopic image display illustrated in FIG. 2, during (n+1)th frame period, the right eye shutter of the liquid crystal shutter glasses ST is open and right eye image data RGBR(Fn+1) are sequentially scanned on the hold type display device DIS2. While the right eye shutter of the liquid crystal shutter glasses ST is open, some pixels, to which the right eye image data RGBR(Fn+1) have not been written yet on the hold type display device DIS2, hold left eye image data RGBL(Fn) which had been already charged in nth frame. Accordingly, the observer can view the image of the left eye image data RGBL(Fn) of the nth frame as well as an image of the right eye image data RGBR(Fn+1) of the (n+1)th frame with his right eye during the (n+1)th frame.
As can be seen from FIG. 2, the observer can feel a pseudo-stereoscopic vision at a time when the left eye image is changed to the right eye image or at a time when the right eye image is changed to the left eye image because of crosstalk between the left and right eye images generated in the hold type display device DISP2.
Thus, in order to improve the degradation of picture quality due to the response time delay of the stereoscopic image display as shown in FIG. 2, US Publication NO. 20070229395A1 disclosed a technique of addressing data more quickly than the related art on a liquid crystal display panel and extending a vertical blanking period. Also, this publication proposed a method of opening liquid crystal shutter glasses ST during a time period obtained by subtracting a liquid crystal response time from the extended vertical blanking period. In proposed method, the vertical blanking period without data is lengthened and an opening duration of the liquid crystal shutter glasses is reduced, thereby making an observer feel flickering. In addition, constructive interference occurs between light that transmits through the liquid crystal shutter and ambient light according to a correlation between an ON/OFF period of the liquid crystal shutter and that of the ambient light such as a fluorescent lamp, making the observer feel flicking more severely.